1. Leakage of refrigerant
[Fault Analysis] After the refrigerant leaks in the system, the cooling capacity is insufficient, the suction and exhaust pressures are low, and the expansion valve can hear a much louder intermittent “squeak” airflow sound than usual. The evaporator is free of frost or a small amount of floating frost. If the expansion valve hole is enlarged, the suction pressure will not change much. After shutdown, the equilibrium pressure in the system is generally lower than the saturation pressure corresponding to the same ambient temperature.
[Solution] After the refrigerant leaks, you should not rush to fill the system with refrigerant. Instead, you should find the leakage point immediately and refill the refrigerant after repair.
2. Too much refrigerant is charged after maintenance
[Fault analysis] The amount of refrigerant charged in the refrigeration system after repair exceeds the capacity of the system, the refrigerant will occupy a certain volume of the condenser, reduce the heat dissipation area, and reduce the cooling efficiency, and the suction and discharge pressures are generally high. At the normal pressure value, the evaporator is not frosted, and the temperature in the warehouse is slowed down.
[Solution] According to the operating procedure, the excess refrigerant shall be released at the high pressure cut-off valve after a few minutes of shutdown, and the residual air in the system can also be released at this time.
3. There is air in the refrigeration system
[Fault analysis] Air in the refrigeration system will reduce the refrigeration efficiency. The prominent phenomenon is that the suction and discharge pressure increase (but the discharge pressure has not exceeded the rated value), and the temperature from the compressor outlet to the condenser inlet increases significantly. Due to the air in the system, the exhaust pressure and exhaust temperature both increase.
[Solution] You can release air from the high-pressure shut-off valve several times in a few minutes after the shutdown, and you can also fill some refrigerant appropriately according to the actual situation.
4. Low compressor efficiency
[Fault Analysis] The low efficiency of the refrigeration compressor refers to the decrease in the actual displacement under the condition of the same working condition, which leads to a response decrease in the refrigeration capacity. This phenomenon mostly occurs on compressors that have been used for a long time. The wear is large, the matching gap of each part is large, and the sealing performance of the valve is reduced, which causes the actual displacement to decrease.
[Solution]
(1) Check whether the cylinder head paper gasket is broken down and cause leakage, if any, replace it.
⑵ Check whether the high and low pressure exhaust valves are not tightly closed, and replace them if they are.
⑶ Check the clearance between the piston and the cylinder. If the clearance is too large, replace it.
5.The frost on the surface of the evaporator is too thick
[Fault analysis] The cold storage evaporator used for a long time should be defrosted regularly. If it does not defrost, the frost layer on the evaporator pipeline will become thicker and thicker. When the entire pipeline is wrapped into a transparent ice layer, it will seriously affect the heat transfer. As a result, the temperature in the warehouse does not fall within the required range.
[Solution] Stop defrosting and open the door to allow air to circulate. Fans can also be used to speed up the circulation to reduce the defrosting time.
6. There is refrigerating oil in the evaporator pipe
[Fault analysis] During the refrigeration cycle, some refrigerating oil remains in the evaporator pipeline. After a long period of use, when there is more residual oil in the evaporator, it will seriously affect the heat transfer effect and cause poor cooling.
【Solution】Remove the refrigerating oil in the evaporator. Remove the evaporator, blow it out, and then dry it. If it is not easy to disassemble, use a compressor to pump air from the entrance of the evaporator, and then use a blowtorch to dry it.
7. The refrigeration system is not unblocked
[Fault analysis] As the refrigeration system is not cleaned, after a certain period of use, dirt gradually accumulates in the filter, and some meshes are blocked, which reduces the flow of refrigerant and affects the cooling effect. In the system, the expansion valve and the filter at the suction port of the compressor are also slightly blocked.
【Solution】The micro-blocking parts can be removed, cleaned, dried, and then installed.
Post time: Nov-16-2021
